1. Field of the Invention
The present invention relates to a sound field control system which produces in a relatively small listening room, a widely and deeply spreading sound field in which a listener feels as if the listener is in a concert hall.
2. Description of the Prior Art
There has so far been realized a sound field control technique which permits the listeners to perceive a space like a hall or a well-designed listening room in a small space by convolving suitable initial reflection sounds in an audio signal (e.g., Sec Japanese Laid-open Patent Publication No. 61-257099/1986).
In the conventional sound field control systems, the number of taps, i.e., the number of reflection sounds, that can be realized is restricted, in view of the limited processing capacity of the hardware and the limited sampling cycle in convolution-calculation of the initial reflection sounds on the audio signal in order to realize for example a feeling of a hall. Furthermore, in adding reverberation sound in order to realize an atmosphere of a church, the amount of possible calculations for forming the reverberation sound is limited for the same reasons as mentioned above, providing insufficient effect.
These effect sounds, such as reflection sound, reverberation sound, etc. show attenuation in their high pass components in comparison with direct sound. Especially, with respect to the components higher than 10 KHz, even if they are cut, the sound is unaffected with respect to the sound field control effect.
Accordingly, a system of operation processing both the direct sound and these effect sounds uniformly with the sampling frequency higher than 40 KHz has a limited cost effectiveness.